This invention relates to improved seal means and more particularly to an improved end face seal means having extended service life for use in a severe service environment, such as a track joint for an endless chain for a crawler tractor.
Track chains operate in extremely abrasive environments and the track joints may be exposed to dust, mud, sand or rock at both cold temperatures as may be found in the arctic regions and hot temperatures as may be found in deserts. The end face seal performs its primary sealing function by mating precisely with and sealingly engaging with the end faces of their associated bushings and because the annular seal rings themselves are accurately positioned and maintained under axial face load by an elastomeric load. It is intended that an effective seal will retain oil within the track joint and will prevent dirt, mud, etc. from entering the track joint.
Among the pertinent prior art patents are Reinsma U.S. Pat. No. 3,390,922 and Reinsma U.S. Pat. No. 3,841,718. Both patents show crescent shaped seal rings in combination with load rings. In U.S. Pat. No. 3,390,922, an O-shaped load ring was employed. This seal purportedly did not work well over widely varying temperature conditions. The seal of U.S. Pat. No. 3,841,718 comprised two thick flanges jointed by a thin hinge section. The load ring was constructed in a canted polygonal shape. The seal did not have sufficient rigidity in cross section to prevent radial and circumferential buckling of the sealing surface of the seal during rotation thereof under load, particularly in larger sizes under heavy loads.
Several seals have been proposed comprised of two members, a first annular part generally L-shaped in cross-section and an annular elastomeric member or load ring. Morley et al. U.S. Pat. No. 4,095,516 shows a L-shaped polyurethane rubber seal with a load ring made from a relatively soft synthetic rubber that is generally parallelogram-shaped in an unstressed condition. Wagner et al. U.S. Pat. No. 4,209,204 discloses a similar seal assembly which includes a relatively rigid annular seal L-shaped in cross section and a pliant annular load ring. Reinsma U.S. Pat. No. 4,331,339 pertains to an end face seal assembly including two components. First, there is a seal ring L-shaped in cross section and made from a thermoplastic resin consisting of a polyamide polymer and a ultra-high molecular weight polyethylene. Second, the seal includes a load ring constructed of an elastomeric resilient material, for example, rubber, and that is of a generally parallelogram shaped configuration.
An object of the present invention is to provide an improved seal means that will function over a wide range of operating conditions, has long life, and is relatively inexpensive to fabricate.
Another object of the present invention is to provide a seal means adapted to be used in particularly demanding working conditions, especially between coupled mechanical parts subjected to an intermittent rotating movement about the same axis.
Yet another object of this invention is to provide multi lip end face seal means adapted to be fitted in the coupling or track joint between the links of a track of tracked vehicles, to prevent abrasive material, earth, sand and water from entering from without, and to seal lubricant within the coupling, such seal means comprising an elastomeric load ring and a seal having at least two lips engaging the face of a bushing in a track joint.
A further object of this invention is to provide multi lip seal means which possesses outstanding abrasion resistance and also considerable elasticity so as to ensure a good radial seal and a good axial seal.
Still a further object of this invention is to provide seal means with its parts held together so that the seal means can be installed readily and correctly without the use of special expedients.
To achieve the aforesaid objects and characteristics, the present invention embodies improved seal means fitted between two coupled mechanical parts rotating about one and the same axis, particularly for application to the tracks of tracked vehicles, characterized in that the seal means comprises an elastic load ring and a seal ring having an "L"-shaped cross section and featuring at least two sealing projections or sealing lips on the base of the L-shaped cross-section of the seal ring for sealingly engaging the face of the bushing. In one embodiment, the load ring is essentially trapezoidal in cross section. In another embodiment, the load ring is essentially circular in cross section.